§ 27.60 TV/DTV interference protection criteria.
Base, fixed, control, and mobile transmitters in the 698-763 MHz,
775-793 MHz, and 805-806 MHz frequency bands must be operated only in
accordance with the rules in this section to reduce the potential for
interference to public reception of the signals of existing TV and DTV
broadcast stations transmitting on TV Channels 51 through 68.
(a) D/U ratios. Licensees must choose site locations that are a
sufficient distance from co-channel and adjacent channel TV and DTV
stations, and/or must use reduced transmitting power or transmitting
antenna height such that the following minimum desired
signal-to-undesired signal ratios (D/U ratios) are met.
(1) The minimum D/U ratio for co-channel stations is:
(i) 40 dB at the hypothetical Grade B contour (64 dBµV/m) (88.5
kilometers (55 miles)) of the TV station;
(ii) For transmitters operating in the 698-746 MHz frequency band, 23
dB at the equivalent Grade B contour (41 dBµV/m) (88.5 kilometers (55
miles)) of the DTV station; or
(iii) For transmitters operating in the 746-763 MHz, 775-793 MHz, and
805-806 MHz frequency bands, 17 dB at the equivalent Grade B contour
(41 dBµV/m) (88.5 kilometers (55 miles)) of the DTV station.
(2) The minimum D/U ratio for adjacent channel stations is 0 dB at the
hypothetical Grade B contour (64 dBµV/m) (88.5 kilometers (55 miles))
of the TV station or −23 dB at the equivalent Grade B contour (41
dBµV/m) (88.5 kilometers (55 miles)) of the DTV station.
(b) TV stations and calculation of contours. The methods used to
calculate TV contours and antenna heights above average terrain are
given in § § 73.683 and 73.684 of this chapter. Tables to determine the
necessary minimum distance from the 698-763 MHz, 775-793 MHz, and
805-806 MHz station to the TV/DTV station, assuming that the TV/DTV
station has a hypothetical or equivalent Grade B contour of 88.5
kilometers (55 miles), are located in § 90.309 of this chapter and
labeled as Tables B, D, and E. Values between those given in the tables
may be determined by linear interpolation. Distances for station
parameters greater than those indicated in the tables should be
calculated in accordance with the required D/U ratios, as provided in
paragraph (a) of this section. The locations of existing and proposed
TV/DTV stations during the period of transition from analog to digital
TV service are given in part 73 of this chapter and in the final
proceedings of MM Docket No. 87-268.
(1) Licensees of stations operating within the ERP and HAAT limits of
§ 27.50 must select one of four methods to meet the TV/DTV protection
requirements, subject to Commission approval:
(i) Utilize the geographic separation specified in Tables B, D, and E
of § 90.309 of this chapter, as appropriate;
(ii) When station parameters are greater than those indicated in the
tables, calculate geographic separation in accordance with the required
D/U ratios, as provided in paragraph (a) of this section;
(iii) Submit an engineering study justifying the proposed separations
based on the parameters of the land mobile station and the parameters,
including authorized and/or applied for facilities, of the TV/DTV
station(s) it is trying to protect; or,
(iv) Obtain written concurrence from the applicable TV/DTV station(s).
If this method is chosen, a copy of the agreement must be submitted
with the application.
(2) The following is the method for geographic separations. (i) Base
and fixed stations that operate in the 746-763 MHz, 775-787 MHz, and
788-793 MHz bands having an antenna height (HAAT) less than 152 m. (500
ft.) shall afford protection to co-channel and adjacent channel TV/DTV
stations in accordance with the values specified in Table B (co-channel
frequencies based on 40 dB protection) and Table E (adjacent channel
frequencies based on 0 dB protection) in § 90.309 of this chapter. Base
and fixed stations that operate in the 698-746 MHz band having an
antenna height (HAAT) less than 152 m. (500 ft.) shall afford
protection to adjacent channel DTV stations in accordance with the
values specified in Table E in § 90.309 of this chapter, shall afford
protection to co-channel DTV stations by providing 23 dB protection to
such stations' equivalent Grade B contour (41 dBµV/m), and shall afford
protection to co-channel and adjacent channel TV stations in accordance
with the values specified in Table B (co-channel frequencies based on
40 dB protection) and Table E (adjacent channel frequencies based on 0
dB protection) in § 90.309 of this chapter. For base and fixed stations
having an antenna height (HAAT) between 152-914 meters (500-3,000 ft.)
the effective radiated power must be reduced below 1 kilowatt in
accordance with the values shown in the power reduction graph in Figure
B in § 90.309 of this chapter. For heights of more than 152 m. (500
ft.) above average terrain, the distance to the radio path horizon will
be calculated assuming smooth earth. If the distance so determined
equals or exceeds the distance to the hypothetical or equivalent Grade
B contour of a co-channel TV/DTV station ( i.e. , it exceeds the
distance from the appropriate Table in § 90.309 of this chapter to the
relevant TV/DTV station), an authorization will not be granted unless
it can be shown in an engineering study ( see paragraph (b)(1)(iii) of
this section) that actual terrain considerations are such as to provide
the desired protection at the actual Grade B contour (64 dBµV/m for TV
and 41 dBµV/m for DTV stations) or unless the effective radiated power
will be further reduced so that, assuming free space attenuation, the
desired protection at the actual Grade B contour (64 dBµV/m for TV and
41 dBµV/m coverage contour for DTV stations) will be achieved.
Directions for calculating powers, heights, and reduction curves are
listed in § 90.309 of this chapter for land mobile stations. Directions
for calculating coverage contours are listed in § 73.683 through 73.685
of this chapter for TV stations and in § 73.625 of this chapter for DTV
stations.
(ii) Control, fixed, and mobile stations (including portables) that
operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
stations (including portables) that operate in the 698-757 MHz, 758-763
MHz, 776-787 MHz, and 788-793 MHz bands are limited in height and power
and therefore shall afford protection to co-channel and adjacent
channel TV/DTV stations in the following manner:
(A) For control, fixed, and mobile stations (including portables) that
operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
stations (including portables) that operate in the 746-757 MHz, 758-763
MHz, 776-787 MHz, and 788-793 MHz bands, co-channel protection shall be
afforded in accordance with the values specified in Table D (co-channel
frequencies based on 40 dB protection for TV stations and 17 dB for DTV
stations) in § 90.309 of this chapter.
(B) For control and mobile stations (including portables) that operate
in the 698-746 MHz band, co-channel protection shall be afforded to TV
stations in accordance with the values specified in Table D (co-channel
frequencies based on 40 dB protection) and to DTV stations by providing
23 dB protection to such stations' equivalent Grade B contour (41
dBµV/m).
(C) For control, fixed, and mobile stations (including portables) that
operate in the 787-788 MHz and 805-806 MHz bands and control and mobile
stations (including portables) that operate in the 698-757 MHz, 758-763
MHz, 776-787 MHz, and 788-793 MHz bands, adjacent channel protection
shall be afforded by providing a minimum distance of 8 kilometers (5
miles) from all adjacent channel TV/DTV station hypothetical or
equivalent Grade B contours (adjacent channel frequencies based on 0 dB
protection for TV stations and −23 dB for DTV stations).
(D) Since control, fixed, and mobile stations may affect different
TV/DTV stations than the associated base or fixed station, particular
care must be taken by applicants/licensees to ensure that all
appropriate TV/DTV stations are considered ( e.g. , a base station may
be operating within TV Channel 62 and the mobiles within TV Channel 67,
in which case TV Channels 61, 62, 63, 66, 67 and 68 must be protected).
Control, fixed, and mobile stations shall keep a minimum distance of
96.5 kilometers (60 miles) from all adjacent channel TV/DTV stations.
Since mobiles and portables are able to move and communicate with each
other, licensees must determine the areas where the mobiles can and
cannot roam in order to protect the TV/DTV stations.
Note to § 27.60: The 88.5 km (55mi) Grade B service contour (64 dBµV/m)
is based on a hypothetical TV station operating at an effective
radiated power of one megawatt, a transmitting antenna height above
average terrain of 610 meters (2000 feet) and the Commission's R-6602
F(50,50) curves. See § 73.699 of this chapter. Maximum facilities for
TV stations operating in the UHF band are 5 megawatts effective
radiated power at an antenna HAAT of 610 meters (2,000 feet). See
§ 73.614 of this chapter. The equivalent contour for DTV stations is
based on a 41 dBµV/m signal strength and the distance to the F(50,90)
curve. See § 73.625 of this chapter.
[ 72 FR 48852 , Aug. 24, 2007]
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